Matt Williams details the possible flaw in Ireland's World Cup strategy

Former Scotland coach and Australian Irish TV pundit Matt Williams has detailed a theory on the possible error in Ireland's Rugby World Cup campaign after their quarter-final exit at the hands of New Zealand.

Head coach Andy Farrell was prepared to play his number one side all through pool play without rotating his key players against the lesser likes of Romania and Tonga.

After being placed in the group of death Ireland weren't prepared to take any chances, but in the end perhaps left the top players without enough fuel in the tank after falling just short to the All Blacks.

Williams believed that the pivotal point that will be raised in the post-mortem is whether they should have played their seconds team in the opening clash against Romania which Ireland won 82-8.

"I think in the review, the question will be, in the last warm-up game against Samoa in Bayonne, they played their seconds team," Williams explained on Virgin Media Sport. 

"Was that the day you play your first team, then give them the week off and don't play them against Romania, and then you get them going [against Tonga].

"Because as Shane has said, they had to peak or be ready for South Africa. And I said this at the time, we will only know in hindsight. But I think it is going to come up in the review.

"That's where the Romania game, where they put 85 points on them, maybe that's it. And maybe we are clutching at straws and maybe it doesn't exist."

Ireland's second unit didn't impress against Samoa in wet conditions during their last warm-up which may have influenced the decision, but also the need to get into form ahead of South Africa surely played a part.

Former international Shane Horgan believed that the circumstances around key players meant that they had to play against Romania and the weight of history also played a role.

"You're trying to balance different things, because you also want to create a momentum, and they did, and a feel good in the camp," Horgan said.

"And you want game time for your key players, some of whom were injured, Sexton hadn't played.

"So there is a balance, and I'm not sure there is a perfect way to do this.

"If there is foolproof way of winning a World Cup everyone would be following it.

"Listen, I thought we had ticked the milestones that Ireland has hit, we'd done all those things. They've done the preparation, they've done what you needed to five yourself a chance of winning the World Cup."

Horgan thought that previous World Cup jitters meant that Farrell wasn't going to take any risks of not picking up the required bonus points.

"I think they had to focus on getting out of that group," he said.

"That's another hangover from never getting out, never getting beyond a quarter-final.

"It's the group of death, Scotland are resurgent and South Africa are the world champions. You're thinking what happens if we don't get the bonus point?

"It happened to me at the World Cup in 2007. We had a terrible result first time out, we got a bonus point, we played Georgia and didn't get a bonus point and nearly got beaten, then we lost against France, and then you're out.

"So I can understand, until Ireland are a little more comfortable in their own skin, I can understand why they did what they did."